1. Narnia is an inexplicable, nonsensical cultural hodgepodge... what's with mixing Greek-mythicals (centaurs, minotaurs, satyrs/fauns) with Norse/Germanic (dwarfs, unicorns, gryphons, dragons, giants) and then mixing those with Bestiary beasts from the Dark Continent like lions, leopards, apes and rhinos? while Middle Earth's cultural inspiration is coherently Germanic and Celtic by design, because it is supposed to offer a mythology for England.

3. Lewis, in A Horse and his Boy, made cheap shots against the Calormenes--who may have been designed to resemble Lewis' perception of Arab, Persian, or South Asian culture perhaps. He did that by trying to portray the Calormene POV, or pretending to, but instead it comes across as a smear. The only sympathetic major character of the Calormenes, Aravis, was the most anti-Calormene. The Calormene culture had no redeeming qualities even from the perspective of one of their own. It felt cartoonish and did not ring true. Tolkien wisely didn't pretend to try to depict the POV of, say, the Haradrim. They were always the Other from the POV of the main characters, except when Faramir speaks of a fallen Harad, wondering about his POV and thoughts before falling. He does so in an empathetic manner, unlike any Narnia character toward the Calormenes.

4. Tolkien's writings were clear about linguistic origins of character names, place names, and invented terms. He invented functional and coherent languages. Lewis, he inexplicably borrowed from Celtic, Greek, Latin, and Turkish IIRC. No reason within the story for drawing from those languages. Aslan's name is Turkish but nothing about his character comes across as anything to do with Turkish culture.

5. Tolkien's invented world had more depth, felt more immersive , than that of Lewis. A bag is like a hole that you can carry with you.